Powdered and beaded zeolite A from recycled coal fly ash with modified iron (III) oxide-hydroxide for lead adsorptions

Abstract

Lead is a highly toxic metal and bioaccumulation through food chain, so it causes human health effects. Thus, contaminated lead in wastewater is required to treat below the water quality standard. This study was to synthesize zeolite A powder (Z), zeolite A powder mixed iron (III) oxide-hydroxide (ZF), zeolite A beads (ZB), and zeolite A powder mixed iron (III) oxide-hydroxide beads (ZFB), characterize with various techniques, investigate their lead removal efficiencies by batch experiments, and study their adsorption patterns and mechanisms. All characterizations of Z have matched to the zeolite A standard (STD) which confirmed the ability to synthesize zeolite A. ZF had the highest specific surface area and smallest pore size than others, and they were mesoporous materials. Silicon, aluminum, and sodium were observed in all materials. The specific crystalline formation of zeolite A was found in all materials corresponding to the STD. Z was a cubic structure representing the specific zeolite A structure, and ZF, ZB, and ZFB had rough surfaces with presenting traces of cubic shapes confirmed being zeolite A. OH, Si or Al–O, and D4R were their main chemical functional groups, and Si–O–Fe was found in ZF and ZFB. In addition, –COOH was observed in ZB and ZFB. The binding energies of Na 1s, O 1s, Si 2p, and Al 2p were found in all materials, and Fe 2p3/2 and Fe 2p1/2 were observed in ZF and ZFB. In addition, Pb 4f7/2 and Pb 4f5/2 were detected after lead adsorptions. The point of zero charges of Z, ZF, ZB, and ZFB were 6.45, 8.65, 6.04, and 8.12. They could remove lead at 50 mg/L of more than 97.5 %. They corresponded to Langmuir and pseudo-second-order kinetic models. Moreover, they could reuse more than 5 cycles. Finally, ZFB is a good offer for real industrial applications.